Hybrid occupant detection system

Abstract

An occupant detection system includes a detection electrode provided in a vehicle seat, a phase difference measuring unit, a direct current measuring unit, and a detecting unit that detects an occupant. The phase difference measuring unit supplies a reference signal comprising a sinusoidal wave to the detection electrode via a resistive element, detects the potential of the detection electrode as an electrode signal, and measures a phase lag time of the electrode signal relative to the reference signal. The direct current measuring unit applies a steady DC voltage to the detection electrode via a resistive element, detects the potential of the detection electrode, and measures time it takes from start of application of the DC voltage to the time when the detection electrode reaches a given potential, as a charge time. The detecting unit detects an occupant based on the phase lag time and the charge time.

Description

[0001]The disclosure of Japanese Patent Application No. 2010-055040 filed on Mar. 11, 2010 including the specification, drawings and abstract is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to an occupant detection system for detecting if an occupant is present in a vehicle seat, and more particularly to an occupant detection system that is able to detect an occupant with stability even when the vehicle seat is wet, for example.[0004]2. Description of the Related Art[0005]In automobiles, detected information as to whether an occupant is present in a seat is used for determining whether an air bag is to be deployed or inflated. A vehicle air-bag system is controlled so that an air bag deploys when an occupant is present in a seat, such as a passenger's seat, at the time of a collision of the vehicle, and the air bag does not deploy when no occupant is present in the seat. Also, in the case where...

AI Technical Summary

Benefits of technology

[0009]The invention provides an occupant detection system that is able to accurately sense the presence of an occupant in a seat and determine the body size or shape of the occupant, and is also able to stably detect an occupant even when there is a disturbance, such as when the seat is wet.

Problems solved by technology

If an electric field is generated around the detection electrode, disturbances arise in the electric field when an occupant is seated in the seat.

Therefore, if the seat gets wet, the impedance around the detection electrode(s) may change, or a wet portion may act as an antenna, which may result in a problem that a determination as to the presence of a seated occupant or whether the occupant is an adult or a child is erroneously made.

However, in a condition where the back and head of the occupant are not in contact with the seatback of the seat, the system may not be able to accurately discriminate between an adult and a child.

Also, a large number of electrodes need to be installed in the seatback portion of the seat, and a switching circuit, or the like, for selectively using the electrodes needs to be provided, thus making the configuration and control of the system complicated.

Also, a complicated operation or processing needs to be performed to calculate the impedance and the phase difference from the measured load current and potential current, determine a threshold value based on the calculated phase difference, and compares the impedance with the threshold value.

As described above, it is difficult or impossible for the known occupant detection systems to accurately determine the body size of a seated occupant (e.g., discriminate between an adult and a child), and also make the determination with accuracy even when there is a disturbance, such as wetting of the seat.

Also, it is necessary to provide a plurality of electrodes for solving the respective problems as described above, which makes the configuration and processing complicated.

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